This invention relates to a device for the evaporation of volatile substances, in particular aromatic substances, insecticides, and the like. In particular, this invention relates to a heating device to be used in the evaporation device, as well as to a process for the production of such a heating device.
Devices for the evaporation of volatile active substances, in particular of aromatic substances and/or insecticides, are generally known. For instance, evaporation devices are known where a small plate impregnated with an active substance, inserted into an evaporation device, is heated by a heating device to evaporate the active substance. A method is also known by which containers containing volatile liquid substances are inserted in a housing of an evaporation device. This container is provided with a wick that conveys the substance to be evaporated out of the container by means of capillary effect. The wick end protruding from the container is next to a heating device with a ceramic heating body so that the volatile substance is evaporated by the heat radiated from the ceramic heating body and can escape into the environment through aeration slits in the housing. European publication EP 1195 169 Al relates to a device of this type and discloses a device for the evaporation of volatile active substances with a housing containing a heating device with at least one heating body that can be heated to an evaporating temperature to evaporate an active ingredient placed in the housing. In practice, the heating body is designed as a ceramic heating body containing an electric resistance element to heat the heating body. The heating element is connected via electric lines to a connector plug installed on the housing. The resistance element is coated at least on part of its surface with a resistance coating that is notched by cutting or grinding at least within a certain area to select a given resistance value corresponding to an evaporating temperature called for by the substance to be evaporated. During the manufacture of the heating device this resistance element is inserted manually into an opening made in the ceramic heating body and is then encapsulated with a material presenting great heat conductivity in order to fix the resistance element securely in the ceramic heating body. This encapsulating with a preferably flame resistant insulation cement is essentially effected manually in order to ensure the precise positioning of the resistance element. At the opposite ends of the opening in the ceramic heating body, and at either side of the resistance element, a slit is made through which the electric lines emerge from the ceramic heating body, e.g. to a switch or to a connector plug.
From EP 0 451 331 Al an evaporation device is known for the evaporation of volatile active substances in which the heating device consists of a ceramic heating body with an electric, imbedded heating coil. This ceramic heating body is provided with a receptacle extending in a straight line at a tangent to its passage channel, so that a heating coil can be inserted and it can be filled with a sealing mass.
Furthermore a ceramic body of this type, combined with an evaporation device for liquid insecticides or perfumes, is also known from EP 0 943 344 Al, EP 0962 132 Al and EP 1 108 358 Al.
An object of the present invention is to create an improved device for the evaporation of volatile active substances, in particular aromatic substances and/or insecticides, that is simple and economical in construction and by means of which a required evaporating temperature can be achieved in a reliable manner.
Another object of the invention is to provide a method for producing such a heating device in the simplest way possible and mostly automatically.